Carbon dioxide absorption methanol process

Abstract

A process is disclosed for the separation of hydrocarbon feed gas mixtures containing carbon dioxide. The process utilizes four distillation units and one absorption unit. The feed gas is fed to the first distillation system where the methane-and-lighter components are separated from the propane-and-heavier hydrocarbons. The top gas product from the first distillation unit is mixed with a portion of the absorbing medium methanol and refrigerated. This mixture is fed to the bottom of the absorber. The gas containing methane, ethane and carbon dioxide flows up the absorber countercurrent to the downcoming liquid methanol. The ethane and carbon dioxide are dissolved by the methanol and exit the bottom of the absorber as a liquid. The methane-and-lighter components are not dissolved by the methanol and leave the absorber as a gas. The bottoms from the first distillation system are fed to a second distillation column where the ethane and carbon dioxide are distilled as a top gas product. This gas mixture and the warmed bottoms from the absorber are fed to a third distillation unit. A small amount of methanol is mixed with the overhead vapor from this distillation unit. The methanol, a polar substance, causes the relativity of carbon dioxide to ethane to both invert. The ethane becomes the lighter component and is distilled from the top of the unit as a gas. The carbon dioxide and methanol bottoms product are fed to a fourth distillation unit where the carbon dioxide is distilled from the methanol.